Phoenix would fall apart. I think because most people here came from somewhere else, if that makes since. As such they have little commitment to staying if they have/had to. Heck it hits 110 degrees and the weathermen are telling people to go to San Diego. Phoenicians are ingrained to get the heck outta dodge and that makes a big mess.

Of course there is 5 million people in the Valley of the Sun, so my point is generalized, tens of thousands if not more are well prepared for anything.

I suppose the positive to a disaster happening here is that the city is an urban sprawl masterpiece. There is CVS, Walgreens, grocery store, megastore, on every street corner laid out in perfect 1 square mile grids. So no one is really more than 5 minutes away from getting last minute supplies if an emergency hit.